The scrapie disease process is unaffected by ionising radiation

The incubation period of scrapie, its degenerative neuropathology and the replication of its causal unconventional virus are all tightly controlled parameters of the experimental disease in mice. Each parameter can vary depending on the strain and dose of virus, on the route of infection, and on the host genotype. Exposure to whole-body gamma-irradiation from Caesium 137 has no effect on the progress or development of the disease, based on the three independent indices of incubation period, neuropathology, or infectibility by high or low doses of virus. These results are based on an extensive series of experiments in many mouse strains and are consistent using different strains (ME7, 22A, 79A, 87V) and doses of virus, routes of infection, timing and dose of radiation (3-15 Gy) administered as single or fractionated exposures with or without bone-marrow (b.m.) replacement therapy. Levels of infection in the spleen are unaltered after lethal whole-body irradiation of the scrapie-infected host, despite several-fold reductions in tissue mass due to the loss of proliferating myeloid and lymphoid precursor cells and their progeny. Contrary to our earlier suggestion, scrapie infection with the 22A virus does not reduce the effectiveness of post-exposure bone-marrow replacements to recolonise an infected host after repeated ionising radiation totalling 15Gy. This work narrows the search for the candidate cells and biosynthetic systems which replicate the virus in the lymphoreticular and central nervous systems. Many programmed cellular events are radiation sensitive but protein synthesis is extremely radioresistant.(ABSTRACT TRUNCATED AT 250 WORDS)